The present invention relates to an electric motor having a rotatably oscillating output shaft, for example for operating a windshield wiper on a motor vehicle, or on a watercraft.
Electric motors are generally built so that the direction of rotation of their output shafts can be reversed by reversing the flow of current through the windings. This requires disconnecting and reconnecting the power source across the motor input terminals, or connecting the motor input terminals to the power source output terminals through a reversing switch. Such arrangements, however, do not provide an adequate means for reversing the direction of rotation of an electric motor output shaft in a rapid and regular sequence such as that needed to operate a device like a windshield wiper on a motor vehicle. Consequently, in mass production, DC electric motors having rotatably oscillating drive shafts must be manufactured in two distinct assembled components. The first component is the motor itself having an output shaft that is intended to rotate continuously in one direction. The second component is a pivot arm and drive shaft assembly which consists of a series of gears and drive arms linking the output shaft of the motor to a rotatably oscillating drive shaft.